fix some more binops

pandas-dev · jreback · Mar 28, 2022 · Feb 17, 2022 · Feb 17, 2022 · Feb 17, 2022
commit dc7517a96a59b7f597bc3b0c241bcad6afe7d779
diff --git a/pandas/_libs/tslibs/nattype.pyx b/pandas/_libs/tslibs/nattype.pyx
@@ -154,6 +154,7 @@ cdef class _NaT(datetime):
 
     def __add__(self, other):
         if self is not c_NaT:
+            # TODO: Cython 3, remove this it moved to __radd__
             # cython __radd__ semantics
             self, other = other, self
 
@@ -180,6 +181,9 @@ cdef class _NaT(datetime):
         # Includes Period, DateOffset going through here
         return NotImplemented
 
+    def __radd__(self, other):
+        return self.__add__(other)
+
     def __sub__(self, other):
         # Duplicate some logic from _Timestamp.__sub__ to avoid needing
         # to subclass; allows us to @final(_Timestamp.__sub__)
@@ -188,6 +192,7 @@ cdef class _NaT(datetime):
 
         if self is not c_NaT:
             # cython __rsub__ semantics
+            # TODO: Cython 3, remove __rsub__ logic from here
             self, other = other, self
             is_rsub = True
 
@@ -231,6 +236,24 @@ cdef class _NaT(datetime):
         # Includes Period, DateOffset going through here
         return NotImplemented
 
+    def __rsub__(self, other):
+        if util.is_array(other):
+            if other.dtype.kind == "m":
+                # timedelta64 - NaT we have to treat NaT as timedelta64
+                #  for this to be meaningful, and the result is timedelta64
+                result = np.empty(other.shape, dtype="timedelta64[ns]")
+                result.fill("NaT")
+                return result
+
+            elif other.dtype.kind == "M":
+                # We treat NaT as a datetime, so regardless of whether this is
+                #  NaT - other or other - NaT, the result is timedelta64
+                result = np.empty(other.shape, dtype="timedelta64[ns]")
+                result.fill("NaT")
+                return result
+        # other cases are same, swap operands is allowed even though we subtract because this is NaT
+        return self.__sub__(other)
+
     def __pos__(self):
         return NaT
 

diff --git a/pandas/_libs/tslibs/period.pyx b/pandas/_libs/tslibs/period.pyx
@@ -1739,6 +1739,7 @@ cdef class _Period(PeriodMixin):
     def __add__(self, other):
         if not is_period_object(self):
             # cython semantics; this is analogous to a call to __radd__
+            # TODO: Cython3, remove this
             if self is NaT:
                 return NaT
             return other.__add__(self)
@@ -1763,6 +1764,11 @@ cdef class _Period(PeriodMixin):
 
         return NotImplemented
 
+    def __radd__(self, other):
+        if other is NaT:
+            return NaT
+        return self.__add__(other)
+
     def __sub__(self, other):
         if not is_period_object(self):
             # cython semantics; this is like a call to __rsub__
@@ -1789,6 +1795,11 @@ cdef class _Period(PeriodMixin):
 
         return NotImplemented
 
+    def __rsub__(self, other):
+        if other is NaT:
+            return NaT
+        return NotImplemented
+
     def asfreq(self, freq, how='E') -> "Period":
         """
         Convert Period to desired frequency, at the start or end of the interval.

diff --git a/pandas/_libs/tslibs/timestamps.pyx b/pandas/_libs/tslibs/timestamps.pyx
@@ -308,9 +308,13 @@ cdef class _Timestamp(ABCTimestamp):
 
         elif not isinstance(self, _Timestamp):
             # cython semantics, args have been switched and this is __radd__
+            # TODO: Cython 3, remove this it moved to __radd__
             return other.__add__(self)
         return NotImplemented
 
+    def __radd__(self, other):
+        return self.__add__(other)
+
     def __sub__(self, other):
 
         if is_any_td_scalar(other) or is_integer_object(other):
@@ -367,10 +371,15 @@ cdef class _Timestamp(ABCTimestamp):
         elif is_datetime64_object(self):
             # GH#28286 cython semantics for __rsub__, `other` is actually
             #  the Timestamp
+            # TODO: Cython 3 remove this, this moved to __rsub__
             return type(other)(self) - other
 
         return NotImplemented
 
+    def __rsub__(self, other):
+        if is_datetime64_object(other):
+            return type(self)(other) - self
+        return NotImplemented
     # -----------------------------------------------------------------
 
     cdef int64_t _maybe_convert_value_to_local(self):